Php类型暗示不与接口和抽象类相处? [英] Php type hinting not getting along with interfaces and abstract classes?
问题描述
我认为在代码示例中查看问题要比首先编写问题容易得多。这是我的PHP代码:
I think it'll be much easier to see the problem in a code example than writing the question in the first place. Here is my php code:
<?php
interface AnInterface
{
public function method();
}
class AClass implements AnInterface
{
public function method()
{
echo __METHOD__;
}
}
abstract class AnAbstractClass
{
abstract public function method( AnInterface $Object );
}
class ConcreteClass extends AnAbstractClass
{
public function method( AClass $Object )
{
$Object->method();
}
}
$Object1 = new ConcreteClass();
$Object2 = new AClass();
$Object1->method( $Object2 );
上述代码会导致以下错误:
The above code causes the following error:
致命错误:ConcreteClass :: method()的声明必须与AnAbstractClass :: method()的声明兼容
Fatal error: Declaration of ConcreteClass::method() must be compatible with that of AnAbstractClass::method()
问题是php似乎没有认识到AnAbstractClass :: method和ConcreteClass :: method的签名是兼容的。难道我做错了什么?谢谢!
The problem is that php doesn't seem to be recognizing the signatures of AnAbstractClass::method and ConcreteClass::method as compatible. Am I doing something wrong? Thanks!
推荐答案
php似乎没有认识到
AnAbstractClass :: method
和ConcreteClass :: method
兼容。
PHP是正确的,它们不兼容。通过只允许 AClass
(或其子代)的实例传递给 ConcreteClass :: method
,你就会破坏 AnAbstractClass
提供的合同:其任何子类必须接受 AnInterface
作为其的参数method()
。
PHP is correct, they're not compatible. By allowing only instances of AClass
(or its children) to be passed to ConcreteClass::method
, you're breaking the contract that AnAbstractClass
provides: Any of its subclasses must accept AnInterface
as an argument to its method()
.
如果您的示例有效,我还有另一个类 BClass
实现 AnInterface
,根据 AnAbstractClass
, method()
应该接受 BClass
的实例,而根据 ConcreteClass
,它不应该接受。
If your example worked, and I had another class BClass
implementing AnInterface
, we'd have a situation where according to AnAbstractClass
, method()
should accept instances of BClass
, while according to ConcreteClass
, it shouldn't.
更改 ConcreteClass :: method
的签名以匹配 AnAbstractClass :: method
。
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